The open toolkit converts this to "→" (which is poor form but whatever). Further processing through Chemistry results in a "#" being used. Tried to converting it to the HTML entity "&rarr;". No dice. Tried converting it back to "&#8594;". That also didn't work. Converting it to "-&gt;" which works but looks awful.

I checked with Arial Unicode MS font and it works better.
The correct version (the above selector works only for the DITA and CSS direct transformation, not the one that uses HTML as intermediate format):